#include <mbgl/test/util.hpp>

#include <mbgl/gl/gl.hpp>
#include <mbgl/map/map.hpp>
#include <mbgl/gl/headless_backend.hpp>
#include <mbgl/gl/offscreen_view.hpp>
#include <mbgl/util/default_thread_pool.hpp>
#include <mbgl/storage/default_file_source.hpp>
#include <mbgl/style/layers/custom_layer.hpp>
#include <mbgl/style/layers/fill_layer.hpp>
#include <mbgl/util/io.hpp>
#include <mbgl/util/mat4.hpp>
#include <mbgl/util/run_loop.hpp>

using namespace mbgl;
using namespace mbgl::style;

// Note that custom layers need to draw geometry with a z value of 1 to take advantage of
// depth-based fragment culling.
static const GLchar* vertexShaderSource = R"MBGL_SHADER(
attribute vec2 a_pos;
void main() {
    gl_Position = vec4(a_pos, 1, 1);
}
)MBGL_SHADER";

static const GLchar* fragmentShaderSource = R"MBGL_SHADER(
void main() {
    gl_FragColor = vec4(0, 0.5, 0, 0.5);
}
)MBGL_SHADER";

// Not using any mbgl-specific stuff (other than a basic error-checking macro) in the
// layer implementation because it is intended to reflect how someone using custom layers
// might actually write their own implementation.

class TestLayer {
public:
    ~TestLayer() {
        if (program) {
            MBGL_CHECK_ERROR(glDeleteBuffers(1, &buffer));
            MBGL_CHECK_ERROR(glDetachShader(program, vertexShader));
            MBGL_CHECK_ERROR(glDetachShader(program, fragmentShader));
            MBGL_CHECK_ERROR(glDeleteShader(vertexShader));
            MBGL_CHECK_ERROR(glDeleteShader(fragmentShader));
            MBGL_CHECK_ERROR(glDeleteProgram(program));
        }
    }

    void initialize() {
        program = MBGL_CHECK_ERROR(glCreateProgram());
        vertexShader = MBGL_CHECK_ERROR(glCreateShader(GL_VERTEX_SHADER));
        fragmentShader = MBGL_CHECK_ERROR(glCreateShader(GL_FRAGMENT_SHADER));

        MBGL_CHECK_ERROR(glShaderSource(vertexShader, 1, &vertexShaderSource, nullptr));
        MBGL_CHECK_ERROR(glCompileShader(vertexShader));
        MBGL_CHECK_ERROR(glAttachShader(program, vertexShader));
        MBGL_CHECK_ERROR(glShaderSource(fragmentShader, 1, &fragmentShaderSource, nullptr));
        MBGL_CHECK_ERROR(glCompileShader(fragmentShader));
        MBGL_CHECK_ERROR(glAttachShader(program, fragmentShader));
        MBGL_CHECK_ERROR(glLinkProgram(program));
        a_pos = glGetAttribLocation(program, "a_pos");

        GLfloat triangle[] = { 0, 0.5, 0.5, -0.5, -0.5, -0.5 };
        MBGL_CHECK_ERROR(glGenBuffers(1, &buffer));
        MBGL_CHECK_ERROR(glBindBuffer(GL_ARRAY_BUFFER, buffer));
        MBGL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(GLfloat), triangle, GL_STATIC_DRAW));
    }

    void render() {
        MBGL_CHECK_ERROR(glUseProgram(program));
        MBGL_CHECK_ERROR(glBindBuffer(GL_ARRAY_BUFFER, buffer));
        MBGL_CHECK_ERROR(glEnableVertexAttribArray(a_pos));
        MBGL_CHECK_ERROR(glVertexAttribPointer(a_pos, 2, GL_FLOAT, GL_FALSE, 0, nullptr));
        MBGL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, 3));
    }

    GLuint program = 0;
    GLuint vertexShader = 0;
    GLuint fragmentShader = 0;
    GLuint buffer = 0;
    GLuint a_pos = 0;
};

TEST(CustomLayer, Basic) {
    util::RunLoop loop;

    HeadlessBackend backend { test::sharedDisplay() };
    OffscreenView view { backend.getContext() };

#ifdef MBGL_ASSET_ZIP
    // Regenerate with `cd test/fixtures/api/ && zip -r assets.zip assets/`
    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets.zip");
#else
    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets");
#endif

    ThreadPool threadPool(4);

    Map map(backend, view.getSize(), 1, fileSource, threadPool, MapMode::Still);
    map.setStyleJSON(util::read_file("test/fixtures/api/water.json"));
    map.setLatLngZoom({ 37.8, -122.5 }, 10);
    map.addLayer(std::make_unique<CustomLayer>(
        "custom",
        [] (void* context) {
            reinterpret_cast<TestLayer*>(context)->initialize();
        },
        [] (void* context, const CustomLayerRenderParameters&) {
            reinterpret_cast<TestLayer*>(context)->render();
        },
        [] (void* context) {
            delete reinterpret_cast<TestLayer*>(context);
        }, new TestLayer()));

    auto layer = std::make_unique<FillLayer>("landcover", "mapbox");
    layer->setSourceLayer("landcover");
    layer->setFillColor(Color{ 1.0, 1.0, 0.0, 1.0 });
    map.addLayer(std::move(layer));

    test::checkImage("test/fixtures/custom_layer/basic", test::render(map, view), 0.0006, 0.1);
}
